1. Field of the Invention
The present invention relates generally to cooking appliances having gas burners with ports aligned to a predetermined relationship with adjacent structures to contribute to piloting of flame kernel patterns.
2. Background Art
Many previously known cooktops using gas burners include circular burners in order to provide a ring of ports that distribute heat at a consistent radial dimension from the burner. Such burners form a circular ring of flame kernels adjacent the outlet of the ports in the burner. Typically, the radial alignment of the ports limits interaction of the flame kernels generated at the ports, and as a result, limits the turndown ratio, the ratio of a burner's energy output per unit time (power, expressed in BTU per/hour) at maximum gas flow rate divided by the power at the minimum sustainable gas flow rate. The resulting flame kernel is then limited by the size of the port, and the limited range of gas flow rates, and is not otherwise controlled for stability. Operation of the burner at the flow rates beyond a limited range within the maximum and minimum flow rates causes lifting of the kernel away from the outlet of the port or flashback in which the kernel germinates within the port, within the primary gas passageway communicating with the port or within both. Such flame kernels are unstable and may be extinguished under variable ambient conditions. Such reactions may reduce the effective heating capacity of the burner under normal operating conditions.
In order to reduce cold spots that may occur centrally over the circular burners and within the ring of flame kernels, some burners have been formed with other configurations. For example, barbeque grills may employ elongated tube burners or U-shaped tube burners to distribute flame kernels throughout a cooking chamber. However, while such burners change the effective heating area in the cooking chamber, the ports in the previously known tube burners may be subject to the same problems of flame kernel instability. Moreover, although it has been known to cover the burner tubes with sear bars or the like in order to adjust heat distribution throughout the cooking chamber flow patterns in the cooking chamber may exacerbate flame instability. In addition, although cooktops have been known to be sealed to prevent the leakage of drips from a cooking surface entering the ports from which the flame kernels emanate, the use of previously known low profile burner structures to improve the stability of cooking vessels and reduce flame exposure often interferes with flame kernel stability.